Prosecco Risotto with Radicchio

Name: Prosecco Risotto with Radicchio
Ingredients: 1 Tbs. unsalted butter; 1 Tbs. extra-virgin olive oil; 1 large shallot, finely chopped; 1 1/2 cups (10 1/2 oz./330 g) Arborio, Carnaroli or other risotto rice; 3/4 cup (6 fl. oz./180 ml) Prosecco; 6 to 7 cups (48 to 56 fl. oz./1.5 to 1.75 l) chicken stock, heated to a simmer; 2 medium heads radicchio, cored and leaves shredded (about 8 cups/8 oz./250 g); 1 Tbs. aged balsamic vinegar; 2 Tbs. mascarpone or heavy cream; 1/2 cup (2 oz./60 g) freshly grated Parmigiano-Reggiano cheese